Modern lathe comprise a tool turret or a similar receiving device for simultaneous reception of a large number of tools. These tools are brought into the working position one after the other by indexing the tool turret, so that a workpiece can be machined by the different tools in turn without tool changing. In order to be able to carry out a final machining of the workpiece as far as possible in a single cut in the lathe, tool holders can also be fitted in the receptacles of the tool turret which can receive driven tools, such as drills, mills and screw-cutting tools. The drive for these driven tools clamped in the tool holder is effected through a drive shaft rotatably mounted in the base holder and whose input end projecting out of the fixing shank of the base holder can be coupled to a rotary drive provided in the tool turret. Since the receptacles for the tool holders in the tool turrets take the most varied forms, the fixing shanks of the tool holders must also be adapted to the receptacles of the tool turret in question. The tool holders themselves are formed in the most varied manner according to the machining requirements. There are for example tool holders in which the driven tools are arranged coaxially or axially parallel or radially relative to the axis of the fixing shank. Furthermore, for certain machining requirements a gear must be provided between the drive shaft of the fixing shank and the tool, with which the speed of rotation of the drive shaft is stepped up or stepped down.
On account of this number of different receptacles and differently formed tool holders, tool holders of modular construction are known (brochure of the firm WTO WERKZEUG-EINRICHTUNGEN GmbH, D-7600 Offenburg, "WTO-Prazisions-Werzeugeinrichtungen" [WTO Precision Tool Devices]), in which the user of these tools can assemble a tool holder corresponding to the current machining requirements from individual modules. Such modules are base holders with variously formed fixing shanks, on to which can be fixed tool heads for drills and mills, tool heads with thread-cutting devices, angle, drilling and milling devices, tool heads with a plurality of spindles, eccentric rotary heads and the like. An intermediate part containing a gear can moreover be fitted between the base holder in question and the tool head in question. There are also intermediate parts with step-up gears and the same with step-down gears, as well as intermediate parts with so-called offset gears, with which the tool head can be mounted radially offset relative to the axis of the fixing shank. The number of the multi-formed modules, from which the user can himself assemble a tool holder matching the current machining requirements, is not specified here exhaustively.
The driven shaft provided in the tool head and also the intermediate shaft in the intermediate part must as a rule be mounted in at least two bearings. In order thereby to achieve a good and solid bearing, especially of the driven shaft in the tool head, which mostly also serves to receive the tool, the two bearings must be arranged at the greatest possible axial spacing from one another. However the axial structural length in the direction of the axis of the fixing shank is thereby increased, so that a tool holder assembled from a plurality of modules projects relatively far out from the tool turret. The greater the projection, the smaller the rigidity of the tool holder in question. With a reduced rigidity the machining accuracy also suffers. Moreover a greatly projecting tool holder leads to long setting traverses, which increase the machining time. Finally, greatly projecting tool holders can also collide more easily with other machine parts.
The invention is therefore based on the problem of providing a tool holder of modular construction for driven tools for use on lathes, of the kind initially referred to, in which, in order to increase rigidity, the modules adapted to fit on the base holder have the smallest possible structural length in the direction of the fixing shank, nevertheless with provision of optimum support, especially of the driven shaft but also of the intermediate shaft.
This is achieved according to the invention in that the driven shaft and the intermediate shaft are provided at the input end on their ends in each case facing the attachment flange with a support pin of the same diameter, each freely projecting beyond the associated coupling part to the respectively adjoining module, and in that the drive shaft and the intermediate shaft are each provided, respectively in the region of the attachment flange and at their ends facing the respective tool head, with a coaxial support bore, in which the support pin of the respectively adjacent module can be inserted with a fit.
Through the fitting engagement of the support pin in the support bore of the drive shaft or of the intermediate shaft there is obtained an optimum support of the driven shaft and also of the intermediate shaft of relatively great axial length, at the same time with shortening of the axial structural length of the tool head or of the intermediate part. The optimum support of the driven shaft of the tool head has above all essential advantages when the driven shaft also includes at the same time the tool receptacle for a drill or mill. The driven shaft then in fact acts as a drilling or milling spindle and a stiffer mounting and hence also a greater machining accuracy result from the additional support of this shaft in the support bore of the adjacent module. Through the additional support of the driven shaft or of the intermediate shaft, bearings provided in the tool head or intermediate part for these shafts can also be arranged at a smaller axial spacing from one another, which leads to shortening of the axial structural length of the individual modules and thus of the complete tool holder. Through this the rigidity of the tool holder assembled from the modules is increased and the further disadvantages associated with tool holders projecting farther are avoided.